1. Field of the Invention
The present invention relates to automatic fluid pressure-intensifying apparatues and method of a hydraulic traveling device, and more particularly, to an automatic fluid pressure-intensifying apparatus and a method of a hydraulic traveling device for increasing a traveling capability or a pulling capability of a heavy equipment under the state that a working device of the heavy equipment does not operate and a traveling device of the heavy equipment operates.
2. Description of the Prior Art
Generally, a traveling device and a working device of a heavy equipment operate by the aid of a hydraulic fluid supplied from a hydraulic pump. Since the heavy equipment is provided with a relief valve for restricting an allowable maximum pressure being established in a hydraulic circuit, any excess hydraulic pressure is not applied to the heavy equipment.
FIG. 1 is a schematic hydraulic circuit diagram of an apparatus for restricting an allowable maximum pressure in a hydraulic traveling device and a hydraulic working device according to the prior art. Referring to FIG. 1, a hydraulic fluid supplied from a hydraulic pump 10 operates a traveling motor 14 in a desired direction due to the change of a flow direction of the hydraulic fluid accomplished by a first control valve 12. Likewise, the hydraulic fluid supplied from the hydraulic pump 10 operates a working device 18 in the desired direction due to the change of the flow direction of the hydraulic fluid accomplished by the second control valve 16. At this time, if a load which is larger than a set pressure of a relief valve 20 is applied to the traveling motor 14 or the working device 18, the relief valve 20 begins to open. In other words, the relief valve 20 opens, and thereby the hydraulic fluid returns a tank 22. As a result, it is possible to prevent the traveling motor 14 or the working device 18 from being damaged. Accordingly, although a load being applied to the traveling motor 14 is increased due to the heavy equipment going up a slope or pulling a heavy object, the load being applied to the traveling motor 14 is restrained at a desired value corresponding to the set pressure of the relief valve 20.
However, in the heavy equipment according to the prior art, the maximum allowable pressure being used to operate the working device 18 is smaller than the maximum allowable pressure being used to operate the traveling motor 14. The set pressure of the relief valve 20 is set on the basis of the maximum allowable pressure used to operate the working device 18. Therefore, the maximum allowable pressure of the traveling motor 14 is restrained to the maximum allowable pressure used to operate the working device 18. Consequently, when a relatively large load is applied to the traveling motor 14 due to the heavy equipment going up a slope way or pulling a heavy object, it is impossible to obtain a necessary traveling capability or a necessary pulling capability by the operation of the relief valve 20 which is set to restrict the allowable maximum pressure used to operate the working device 18 at a predetermined value.